I respectfully disagree. I have catless dps with the secondaries still there and there is a noticeable difference at idle as well as while driving. I would have to think deleting the secondary cat would only increase the sound a bit more. I'm not saying it's a huge difference from stock, but noticeable IMO.

E90 or E92? E92's have an x-pipe, and E90s have a resonator; E90's definitely sound stock even with downpipes + secondary delete. FYI, if the wastegate rattle "fix" is enabled on your procede you will have a deeper exhaust note than in the default position.